Preparation of wood pulp cellulose for nitration



Sept. 18, 1945. w. E. SILLICK PREPARATION OF WOOD PULP CELLULOSE FbR NITRATION Filed Feb. 24, 1943 WILLIAM E. SILL/CK INKENTOR ATT NI EY. S

Patented Sept. 18, 1945 PREPARATION OF WOOD PULP CELLULOSE FOR NITRATION William E. Sillick, Rochester, N. Y., assignor ,to;

Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application February 24, 1943, Serial No. 476,980

Claims.

This invention relates to a method of preparing wood pulp cellulose for nitration in which the wood pulp, in a disintegrated or loosely fibrous form, is subjected to a rolling action to form lightly compacted rods or worms of the cellulose.

The form which cellulose should take for nitrationprocesses, particularly in processes of nitrating wood pulp, has been a subject for much investigation. Some investigators in this field have suggested a method of nitrating .wood pulp by immersing wood pulp sheets directly in nitrating acid-Other have suggested formation of the wood pulp into chips and treating those chips with nitrating acid. Various other physical forms for wood-pulp to be nitrated have been suggested, such as small bits, dust, or loosely separated fibers. Some of these physical forms of wood pulp are adapted only for the preparation of high viscosity cellulose nitrates. Other of the suggested-forms of pulp have never been found to be suitable in nitrating processes because of the difficulty of penetration of the acid throughout the mass of cellulose. Sti1lother of the suggested forms have been objectionable because ofthe bulkiness, dustiness, and absorbency 'resulting. in diminished production with a given amount'of equipment and, also, necessitating the use "of 1a considerableexcess of acid to promote the-nitration processes. i

. Thegdisintegrationof wood pulp into a bulk mass of separated fibers, described in disclosures such as British Patent 336 of 1891, U. S. Patent 480,588; or German Patent 300,844, has resulted in material whichhas exhibited desirablepropertieszin various vnitrating processes. This disintegrated material, however, does have the disadvantages of dustiness and, because of bulkiness,; necessitates large bins for a given weight. Also'for certain nitrating processes in which the absorption of acid should be only moderate this material has not worked out so well. Although this disintegrated material is completely penetrated by a nitrating acid, because of the separation of the "W006. pulp into substantially individual fibers, nevertheless, bulkiness or dustiness results :which apparently has ruled out this disintegrated pulp for nitrating purposes to any substantial extent. Few, if any, commercial processes :at the present time use a bulky disintegrated wood pulp asthe material to be nitrated.

An object-of my invention isto provide a wood pulp cellulose having a physical-form suitable ing processes, whether to prepare high or low viscosity nitrate and whether to prepare a high- 1y nitrated cellulose; such as of the gun cotton graphic film base. Anotherobjectof-my invention is to prepare a wood pulp cellulose having advantages as to bin capacity. lack of dustiness, and ease of loading intothe nitrating facilities. A still further object of my invention'is to employ for a nitrating processa cellulose in a physical form-in which the absorption of acid is such as to permit'the use of relatively low ratios of acid to cellulose in the nitration tanks, such asless than ordinarily employed-in the nitrating of cotton linters. r

I have found that the varlousdisadvantages residing in the use of a loosely flufied wood pulp for nitrating purposes may be substantially eliminated by subjecting thatflufied material to a rolling action such as by subjecting it to'the action of two surfaces-either (1) moving in opposite direction, (2) one stationary and the other moving, or (3) both moving in the same'direction butatdifferent rates of speed; This action forms the cellulose into' lightly compacted rods or worms having but a small diameter and a length several times the diameter, thus making for a large number of long rolled units. These units fit well together in a nitrating pot, exhibit 1itt1e,'if any, dustiness, and are uniformly penetrated by the nitrating acidwithout soaking up that acid to an undesirable degree. This formation of rollsor the so-called worms'may, for example, be accomplished by spreading a fluffed wood pulp cellulose in a thinlayer upon a surface and passing a ,clothsheet, such as flannel, which clothsheetpresses down'on the cellulose, thereover at a-rate of .speed different from that of the surface upon which the wood pulp is deposited. v

In the, accompanying drawingFig. 1 illustrates an apparatus adapted for the preparing of the Wood pulpprolls in-accordance with my invention. I and 2 are-each endless belts of the width desired, such as 18 inches or 2 feet up to 6 feet or more, moving in the same direction. The belt I. is moved at a more rapid rate than endless belt 2, such as for instance, 20 to 40. feet per minute compared toa speed of 10 to 20 feet per minute for endless belt 2. Ducts 3 are for the purposeof admittingfluffed wood pulpcellulose to the endless beltsas shown, while conveyor 4 receives the rods or worms" after their formafor use in any of the ordinarily employed nitrattion and carries them through adrier or directly to their storage bin. The supporting rollers shown are preferably adjustable so that the distance between the belts I and '2 may be adjusted, depending upon the density of the pulp which is fed in and the depth of the layer which is formed on belt 2 before being led through the rolling portion of the machine.

planjlvi'ewgiofla sectioni'of the'coriveyor g' the'carrying of the rods-or worms thereby. In practice the units would preferably combination of apparatus is giyento-illustrate the purpose at hand. Obviously, other combinations involving the use of tw'osuttaoes n oviz-if' at different rates may be employed to form the} fiuffed pulp into rods or rolls in accordance with my invention.

A flufied cellulose which use in the formation of rolls in accordance with srae ite p is marketed). into a d sinteeram such. as. a sprout-wheres attri-' Biitisii r terit rieopt .8.9.1. pr inIU. s. Patent.

of lgellner, An apparatus. which fluffs lI'llJQ its in vi dual fibers isv suitable e filmed wood p W hm d s red. ar a when. m be eat d inasq-qreem -w t mr nv ti tc m: eesti'th i ma r 1 ther te. As the saeiera r emelo eclia trata s n som types 9 nitrOr.

2.1141 9%; cases it is desirable that the wood-pulpwhichis emnlerediesthcstami amatcria s naccordenc with; m inYention;.-;he a iig'h bu ts mall rompt n oiimnur c there In .cescswherecclc not mportant. crd unbleached pr .nartiallyihleached P111112:

may be cmpl x di Thenu nenmloycd-for.nitrate. ingZi-S cithensulfiteonkrattpuip; ,Eithcrof these; maiiibeused Lathe method of: myiIlVeIbtiQniL one type fnitra ina pmpess; to. which my venticm-smaysbe adapted isi thatcdescribedi. and claimed in'HLISLiPa-tent 2..1.18, 2;'l.5. for themakin oficellulose nitrateiwhiclrisnitrated. toe nitrogen. content. of approximately. 1 1:5. to; l2 -.3.;%.-,. partioue. larbv. alowvvi'sc osityz cellulose. nitrate is; 16:- s-iredr; After nuflineiaihigh. vu-lcellulose w ood pulp and-Jormingitjntqrodsnonfwormstas described herein; these maygcbeiemployedcastheistartingo materiat 'for..;the nitration described that patent. a.highly'gnitratedcelluloseis. desired the ibell-lllOSQa. material prepared. accordance with.=my-- invention-in the. form. of rodsr or .;rol;ls. maybe. employed as thestarting material any ot the processes.-.ordinarilyeemployed.zfor that punzuziseg :forminstance, by: utilizing a- .nitrating mixture comprising 28% nitric acid, 55% sulfuric acid;- and :17 water thecellulose in the. f ormimparted miaccordance with .myinvention will not mat or form densemasses. in .the. nitrating apparatus,-nor will therebe any .dustiness or loss ofv cellulose. resulting. from handlingn: .Also, the operations r.=oft..stabilizing and dehydrating. the nitrateewood pulp; may. be handled with facility, thelproducii not being bulky or difiicult to...treatl liarious forms of. cellulose; assuszxestedin the priorsant, rare adapted to. .varioustypesoflnitrae; titan; i For; ins ance,- some forms. of. cel ul sev sue: s ated wou d. my. be'suitable .for; the. prepare; .of high ;.ifssies tincell ose. nit ate Din r teased qel alqsawc llsi apt-. 2 1 1. able maybe obtained, for instance, by Sheet lwhichfisfa usualf form inv alhieh, s.: el1 los ..ceatet t.. these;

iulose oi. seed:

processes in which a highly nitrated product is obtained. The rolls of cellulose or worms, such as prepared in accordance with my invention, however, are adapted for various types of nitrating processes and will be found to be economical in that a relatively low ratio of acid to cellulose may be employed in the nitrating pot.

iks fan exampleiof forming a. cellulose nitrate in--=-a'"ccorda'nce with my invention, a, sulfite pulp I having a high 04-0811111056 content and in sheet be more densely associated than shown.

form, was passed through a disintegrating mawhich -flqu-ffed the pulp, producing a matea setup which has been found to'b' suitabletor; rial having a bulk value of 1200 units, nitration grade cotton linters being taken as 800 units, =these units -bei-ng; based on volume per unit -wfeight; flufled cellulose was then spread 'on"a'cloth-covered table in a layer about 1 /2 qinchesnthichand the l y r w s rolled under a is quite suitable for firm cloth-covered surface for a distance of about 9-feet with a pressure upon the pulp layer ing an apprcciable. all-19. 1 1 1; of dust. The. bulk valu the cellulose Was reduced from about. 12cc units to; about 7-90.- unillst This reduction in b ull;;,was sufiicien-t, to yielda material. which.

; Was: ea ily; hand ed; in. s nd rd wei h n coutei-ncrs. and which. .cul ribe charged; into the. nitratina cs els normal rates crspeed With.- no .di icu tr. fr aflca in orifirin The cellue .8 material Was nitratedin accordance with the method described in; I..-.S;'.; Baheut Alla-.275. of;

Talbot retc rsdto abov and the; finalproduch;

after wasbi ianstabil insiand dehydretina. was.

fcundato have ich racteristicssatisfactoryfor a:

produc ofith'is hind. isidesirablein passinaxthe flufied pulp. in laxeniormlbetwcen suriaccsin accordance with my: invention that a moderate amount-of; pres: sure-,beexerted therein..- It desirable thatthesesurfaces; be adiustable so. astecontrol the specing of these surfaces, depending onsthe. thickness.- ofithe layer; passed. therethroughi Alsdbythis meanslthe degreel iii-compactness ofillhe rods or; rolJedunits-may be regulated; Ordinarily a.pressure.s,elected.from .th'e.-range.2+.e30;. pounds per square ifo'otwill .be-most: suitablaas theirlensity. ot.,:the; fiuffedipnln iasubstantially decreased therebyi withoutexcessive. compacting. Ifgthe. pressure .i& too. great. the amount of compacting: lLbe: suchrthat penetration .of the. rolled by... thenitratingacids betdifitcult; If; on. the. other hand. too slight :a pressure is=emp1oyed verylittle compacting results and; the valuable features of mymventi'on will notberealized to thefull extent... y. g

. ordinarily cloth surfaces; are quitesuitable tor preparing therolled accordance with my invention. Forz'mstance flannel, canvas; orsome other-cloth especially of good wearing qualities is. suitable .for-euse. .The surfaces, however, may beof, any material...sufiiciently rough-that slid-l ins doesnotnoccur which would-defeat the. ob.

ject of the invention.

, Althou h the drawing; shows rollsto. impart risisli rtc he can. sue ae s picturesihflrewther l mee s le es hi$;.-fi s chas pl es r;

boards presenting a smooth, rigid surface, may be employed instead. It is desirable that the pulp be dried after the passing between surfaces rather than before, as I have found the pulp behave better in rolling into rodlike units when not completely bone-dry.

Iclaim:

l. The method which comprises passing a uniformly, loosely flulfed air-dry wood pulp having a bulk value of approximately 1200 units between surfaces having motion relative to each other, which lightly press upon the pulp so as to form the pulp into dry loosely rolled units having a bulk value approximating 700 units.

2. A method of preparing cellulose nitrate from wood pulp, which comprises passing dry Wood pulp sheet through a disintegrating mill to uniformly, loosely fluff pulp to a bulk value of approximately 1200 units, passing the uniformly, loosely flufied air-dry pulp thus obtained between surfaces having motion relative to each other, whichlightly press upon the pulp, to form the pulp into dry loosely rolled units having a bulk value approximating 700 units and nitrating the dry loosely rolled units thus obtained.

3. The method which comprises passing a uniformly, loosely fiufied air-dry wood pulp having a bulk value of approximately 1200 units between surfaces moving in opposite directions which lightly press upon the pulp so as to form the pulp into dry, loosely rolled units having a bulk value approximating 700 units.

4. The method which comprises passing a uniformly, loosely fiuffed air-dry wood pulp h'aving a bulk value of approximately 1200 units between surfacesone of which is stationary and the other moving, which surfaces lightly press upon the pulp so as to form it into dry, loosely rolled units having a bulk value approximating 700 units.

5. The method which comprises passing a uniformly, loosely fiufied air-dry wood pulp having a bulk value of approximately 1200 units between surfaces moving in the same direction but at different rates of speed, which surfaces lightly press upon the pulp so as to form it into dry, loosely rolled units having a bulk value approximating 700 units.

WILLIAM E. SlLLICK. 

